The term plastics is used instead of polymer to indicate a specific category of high molecular weight materials that can be shaped using a combination of heat, pressure, and time. All plastics are polymers, but not all polymers are plastics. In this text, we will discuss the major plastics that are useful as packaging materials. To a limited extent, we will discuss cellophane, which is a wood-based material that is a polymer, but not a plastic. We will also discuss adhesives, which are polymers and may or may not be plastics, but which are very useful in the fabrication of plastic and other types of packaging.

    Table 1.1 Approximate Dates of Introduction for Some Common Plastics

    Packaging started with natural materials such as leaves. From there, it progressed to fabricated materials such as woven containers and pottery. Glass and wood have been used in packaging for about 5000 years. In 1823, Durand in England patented the “canister,” the first tin-plate metal container. The double seamed three-piece can was in use by 1900. Paper and paperboard became important packaging materials around 1900. As soon as plastic materials were discovered, they were tried as packaging materials, mainly to replace paper packaging. Use of cellophane, which is a polymer but not truly a plastic, predated much of the use of plastics.

    The use of plastics in packaging applications began, for the most part, after World War II. Polyethylene had been produced in large quantities during the war years, and it became commercially available immediately after the war. Its first application had been as insulation for wiring in radar and high frequently radio equipment. It was soon found that it could be formed easily into various shapes useful for packaging. An early application was in bread bags, replacing waxed paper. Polyethylene coatings replaced wax in heat-sealable paperboard. As a coating, it was also combined with paper to replace waxed paper and cellophane. The driving force behind the expansion of polyethylene use was to obtain a resealable package as well as a transparent material that allowed the product to be visible. Polyethylene remains the leading packaging plastic because of its low raw material price, versatile properties, and its ease of manufacture and fabrication.

    The growth of plastics packaging has accelerated rapidly since the 1970s, in large part because of one of the main feature of plastics – low density. This low density made the use of plastics attractive because of the weight savings, which translates into energy savings for transportation of packaged goods. In addition, plastic packages are usually thinner than their counterparts in glass, metal, paper, or paperboard. Therefore, conversion to plastic packaging often permits economies of space as well as of weight. Savings in amount distribution packaging needed may also result. Another important property is the relatively low melting temperatures mean less energy is required to produce and fabricate the materials and packages. While use of plastics in all applications has grown rapidly during this period, the growth in packaging has outpaced the growth in other sectors. Packaging is the largest single market for plastics – packaging accounted for about 28% of all thermoplastics and engineering resins used in North America. According to The Association of Plastics Manufacturers in Europe, APME, packaging accounted for 37.2 percent of all plastics used in Europe in 2002 and 2003 (www.apme.org).

    Many of the early applications of plastics were in food packaging. The substitution of plastic films for paper in flexible packaging led to the development of many new combinations of materials, and to the use of several polymers together to gain the benefit of their various attributes. The development of flexible packaging for foods picked up speed in the late 1940s and 1950s as the prepared foods business began to emerge. Milk cartons using polyethylene coated paperboard were introduced in the 1950s. Here the driving force was economics: glass is more expensive in system sense, breakage of glass on line required extensive cleaning, and returnable bottles brought all sorts of foreign objects into an otherwise clean environment.

    In industrial packaging, plastics were used early as a part of multiwall shipping sacks that replaced bulk shipments, drums, and burlap sacks. Again, polyethylene film was the predominant material used. Cement in 110kg (50lb) bags became a major application of polyethylene film in industrial sector. The polyethylene liner protects the cement from moisture that would cause it to solidify. Another large use of plastics in industrial packaging is an cushioning to protect goods from vibration and impact during shipping. Polystyrene, polyurethane and polyethylene foams, along with other polymers, are used as cushioning, competing against paper-based cushioning materials.

    Medical packaging has been another big user of plastics. As converting techniques improved, so that accurate molding of small vials could be accomplished at low cost, and as new polymers became available with the necessary characteristics, plastics have been substituted for glass in many applications. As medical procedures became more complex, more disposable kits were introduced, designed to have complete sets of equipment for specific procedures. These kits requires special packaging to keep the part organized and easily useable. Here thermoformed trays became standard, so that kits of pre-sterilized, disposable instruments and supplies, in the proper varieties and amounts, can be readily assembled. The plastics packaging allows the sterilization to occur after the packaging is sealed, thus eliminating the possibility of recontamination after sterilization, as long as the package remains intact. Sterilization with ethylene oxide is facilitated by use of spun-bonded polymeric fabrics. Radiation sterilization depends on the use of polymers that remain their integrity after exposure to ionizing radiation.

    The energy crisis in the 1970s, while at first leading to attacks on plastics as users of precious petroleum actually accelerated the movement to plastic packaging because of the weight reduction possible. Many metal cans and glass bottles were replaced by plastic cans and bottles, and in many cases changes in packaging design moved the product out of rigid packaging altogether, into flexible packaging, which more often than not was made of plastic. Similarly, some metal drums were replaced by plastic drums. A major driving force was to reduce to fuel used to for transportation of both packages and packaged goods by reducing the weight of the packaging. One important example is the introduction of the plastic beverage bottle.

    Environmental concerns of the 1980s and early 1990s, caused by littering issues and a perceived lack of landfill space, caused a major rethinking of the plastic packaging in use, Companies that used plastics had to defend the uses that were in place, and justify new applications. The result was a more responsible approach to packaging in general, by most companies. As politicians and the public became more informed about the truth concerning plastics and the environment, the issues receded from the forefront, although they have not disappeared altogether. Today, plastic packaging has earned its position as one of the choice of the package designer. Decisions about which material should be used require consideration of (1) product protection requirements, (2) market image, (3) cost, and (4) environmental issues.